This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Rapidly frozen biological samples show near-to-native preservation of structure, but this virtue comes at a price;contrast in frozen-hydrated specimens is modest, and the samples are very sensitive to the electron beam, so it is difficult to use electron microscopy to identify areas of interest in such specimens. We are therefore trying to pre-screen frozen-samples by light microscopy, mapping areas of interest on a TEM-finder grid. Our approach has been designed to make use of tools that are commonly available in cell biology, e.g., GFP-labeled proteins of interest and a conventional fluorescence light microscope. To maintain sample quality during screening, however, one must maintain sample temperature less than or equal to -130 degrees C.